/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.core.codec;

import java.io.ByteArrayInputStream;
import java.util.Map;

import org.reactivestreams.Publisher;
import reactor.core.publisher.Flux;

import org.springframework.core.ResolvableType;
import org.springframework.core.io.ByteArrayResource;
import org.springframework.core.io.InputStreamResource;
import org.springframework.core.io.Resource;
import org.springframework.core.io.buffer.DataBuffer;
import org.springframework.core.io.buffer.DataBufferUtils;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.MimeType;
import org.springframework.util.MimeTypeUtils;

/**
 * Decoder for {@link Resource}s.
 *
 * @author Arjen Poutsma
 * @author Rossen Stoyanchev
 * @since 5.0
 */
public class ResourceDecoder extends AbstractDataBufferDecoder<Resource> {


    public ResourceDecoder() {
        super(MimeTypeUtils.ALL);
    }


    @Override
    public boolean canDecode(ResolvableType elementType, @Nullable MimeType mimeType) {
        Class<?> clazz = elementType.getRawClass();
        return (clazz != null &&
                (InputStreamResource.class == clazz || clazz.isAssignableFrom(ByteArrayResource.class)) &&
                super.canDecode(elementType, mimeType));
    }

    @Override
    public Flux<Resource> decode(Publisher<DataBuffer> inputStream, ResolvableType elementType,
                                 @Nullable MimeType mimeType, @Nullable Map<String, Object> hints) {

        return Flux.from(decodeToMono(inputStream, elementType, mimeType, hints));
    }

    @Override
    protected Resource decodeDataBuffer(DataBuffer dataBuffer, ResolvableType elementType,
                                        @Nullable MimeType mimeType, @Nullable Map<String, Object> hints) {

        byte[] bytes = new byte[dataBuffer.readableByteCount()];
        dataBuffer.read(bytes);
        DataBufferUtils.release(dataBuffer);

        Class<?> clazz = elementType.getRawClass();
        Assert.state(clazz != null, "No resource class");

        if (InputStreamResource.class == clazz) {
            return new InputStreamResource(new ByteArrayInputStream(bytes));
        } else if (clazz.isAssignableFrom(ByteArrayResource.class)) {
            return new ByteArrayResource(bytes);
        } else {
            throw new IllegalStateException("Unsupported resource class: " + clazz);
        }
    }

}
